Fat and weak-willed, he was often bullied. His depressed hikkikomori cousin made him wonder about the worth of his life, and that of others.

Yet, after Honda's battle, he stabbed, non-fatally, the teacher who had used her, with her knife that she had given him. He discussed his views about the lack of importance of individual human lives with Captain Tanaka, as well as about sacrifices. He wondered if he could bring himself the courage to fight and kill another human, even knowing that the entire world's fate depend on it, and asks Tanaka to kill him and replace him if he fails to it. Before his battle starts, he shows himself to the opponent robot, and their pilot, a girl, does likewise, and shows him the many cuts and slits along her arm. After this moment Kirie finally finds his resolve to fight. They then return to the inside of their robots and begin to battle. His battle has not been detailed because the next chapter skips ahead, but he obviously won the battle. His chair was a fancy stool.

In the anime, Kirie lacks the will to fight, but his opponent commits suicide in front of Zearth, ripping out and crushing its own cockpit. Despite the technical win, Kirie does not die, and in fact remains pilot for a second match. Curoiusly, Kirie is revealed to be a natural in piloting Zearth as he quickly and swiftly overwhelms the enemy robot. After the fight, Kirie confirms his suspiciusness of Machi's and unveils her true identity. He then dies quietly amid the commotion as Kanji restrains a furious Anko, who had begun to attack her.